As a noun, ache means a continuous dull pain, as a verb, to suffer from a continuous dull pain; in the International Phonetic Alphabet, its pronunciation is /eɪk/ — as in rake for example.

As a noun, ache is from Old English æce, as a verb, from Old English acan. According to the Oxford English Dictionary (3^rd edition – 2009), æce is from acan, a Germanic verb cognate with Middle Low German ēken, to discharge pus, and with the base of Middle Dutch akel, injury, harm.

Before being written ache, the verb was, correctly, ake. The noun was ache with ch pronounced as in church, which explains the following pun on the letter name H in Much adoe about Nothing (Quarto 1, 1600), by the English poet and playwright William Shakespeare (1564-1616):

– Beatrice. Tis almost fiue a clocke cosin, tis time you were rea-
dy, by my troth I am exceeding ill, hey ho.
– Margaret. For a hauke, a horse, or a husband?
– Beatrice. For the letter that begins them al, H.

The pair ake–ache (verb/noun) was therefore similar to the pairs bake–batch, make–match, wake–watch, break–breach, speak–speech and stick–stitch.

Around 1700, the noun ache began to be phonetically influenced by the verb, but, finally, instead of both being written ake (which would have reflected the pronunciation that has survived), both verb and noun are now written ache (reflecting the pronunciation that has become obsolete).

The English lexicographer Samuel Johnson (1709-84), known as Dr. Johnson, is largely responsible for this paradoxical result; ignorant of the history of the words, he mistakenly assumed the derivation to be from Greek ἄχος (= ákhos), meaning pain, distress, in A Dictionary of the English Language (1755):

– Ache. n.s. [ace, Sax. ἄχος, Gr. now generally written ake, and in the plural akes, of one syllable; the primitive manner being preserved chiefly in poetry, for the sake of the measure.]
– To Ache v.n. [See Ache.]
– To Ake. v.n. [from ἄχος, Gr. and therefore more grammatically written ache. See Ache.]

“The primitive manner [that must be] preserved chiefly in poetry, for the sake of the measure” is the dissyllabic pronunciation of the plural noun aches, as though it were written aitches, required by the metre in passages such as the following from A Description of a City Shower, by the Irish satirist, poet and Anglican cleric Jonathan Swift (1667-1745), first published in The Tatler: or, Lucubrations of Isaac Bickerstaff, Esq (London) of 17^th October 1710:

(1777 edition of The Tatler)
A coming Show’r your shooting corns presage,
Old aches throb, your hollow tooth will rage.

In several later editions of this poem or of The Tatler, because the plural noun aches was no longer understood as dissyllabic, the passage has been modified, for example in The Works of the Rev. Jonathan Swift (London, 1808):

A coming shower your shooting corns presage,
Old aches* will throb, your hollow tooth will rage.

The editor of the text wrote in a footnote:

* In the old folio, and first octavo, this word was used as a dissyllable, “Old a-ches throb,” &c. and so it has continued in all the subsequent editions both of the Tatler, and Swift’s “Works,” till the collection of the English Poets was published in 1799 by Dr. Johnson.

However, this passage was modified before 1799; in A letter, from Germany, to the Princess Royal of England; on the English and German languages (Hamburg, 1797), the English author Herbert Croft (1751-1816) explained:

Much, of what the poet and the linguist wish to see, is, now, altered. […] In the booksellers’ edition, I remember that, when Swift writes, according to the custom of his day or to his opinion, in The city-shower, “old aches throb” (aches two syllables), they have the assurance to sell us “old aches will throb.”

In the early 19^th century, John Philip Kemble (1757-1823), English actor and manager of Covent Garden Theatre in London, revived the dissyllabic pronunciation of the plural noun aches in The Tempest, by Shakespeare, in which Prospero says to Caliban:

(Folio 1, 1623)
If thou neglectst, or dost vnwillingly
What I command, Ile racke thee with old Crampes,
Fill all thy bones with Aches, make thee rore,
That beasts shall tremble at thy dyn.

The playhouse burned down in 1808; the increase in prices after the opening of the new theatre in 1809 led to riots known as Old Price, or OP, riots. The OP rioters imitated John Kemble’s pronunciation; on 26^th September 1809, the Kentish Gazette (Canterbury, Kent) reported that on Thursday night, at Covent Garden:

Among the Placards were the following:—
“Make no noise, John’s head aitches.”
                     “Kemble! hear
                       John Bull advises,
                    To save your fame,
                      Reduce your prices!”

In the same number, this newspaper mentioned that, on Friday night:

Among the placards, the following were the most conspicuous—
“A representation of Kemble suspended from a gallows, motto, A cure for my aitches.”—“John Bull, versus King John.”—“Support King George, resist King Kemble.”